ML20058L168
| ML20058L168 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/25/1974 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9105080340 | |
| Download: ML20058L168 (2) | |
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s NORTHERN STATES POWER COMPANY Minneapolis, Minnesota 55401 M.
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March 25, 1974
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- $5 l Mr. J. F. O' leary, Director h/k q,
Obe 4 Directorate of Licensing R j /p 3 /
Office of Regulation 2
3' United States Atomic Energy Commission Washington, D. C.
20545
Dear Mr. O' Leary:
?DhTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Slow Closure of a Main Steam Isolation Valve A condition occurred at the Monticello Nuclear Generating Plant which we are reporting to your office in accordance with Section 6.7.B.1, Abnomal Occurrence Reports, of the Technical Specifications, of Provisional Operating License DPR-22.
On March 15, 1974, during routine surveillance testing, MSIV 2-80C closed in 10 seconds. This closure was in excess of the allowable Technical Specification of 3-5 seconds closure. An inspection of the valve revealed some galling of the yoke rods.
It was noted that the yoke rods were not riding uniformly on the rollers attached at the top of the foke which would indicate possible metal to metal contact between the spring support yoke and the yoke rods. Corrective maintenance will include readjusting the rollers to obtain clearance between the yoke and the yoke rods, burnishing the galled areas on the yoke rods, and lubricating the contact areas between the rollers and the yoke rods. This work will be completed during the course of the current refueling outage.
This occurrence did not effect safe operation since the time closure of the outboard valve MSIV 2-86C was within the limits of the Technical Specifications.
This is the second incident of slow closure due to misalignment of rollers with respect to yoke rods. A prior occurrence was reported to your office in our letter dated August 10, 1973. NSP efforts to establish improved Main Steam Isolation Valve reliability are outlined in that letter.
In response to the previous occurrence the MSIV Surveillance procedure was y050003407493pg ADOCK 05000263 CF
established which specifically includes checking for possible yoke rod interference and proper roller contact. Work in accordance with this procedure will be performed on all MSn"s during the current refueling outage. This work will be repeated each refueling outage and following maintenance on the valves.
Yours very truly, W 8.'
i L. O. Mayer, PE Director of Nuclear Support Services LOWkik cc: J G Keppler G Charnoff Minnesota Pollution Control Agency Attention: E A Pry:ina l
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